UMLet 13.0 -- check for new versions -- read the FAQ

Double-click on an element to add it to the diagram (or use drag&drop)
Use Ctrl+Space in text panel to get context-sensitive help
Use the "layer=" command to move elements to front/to back
Lasso with Ctrl+Mouse -- zoom with Ctrl+MouseWheel
Let UMLet generate diagrams from your source code or class files in the file menu..
Advanced: "Custom Elements > New..." lets you create entirely new element types

If you like UMLet, please "star" it at Eclipse Marketplace. We really appreciate it!